Clamp mechanism for a lifting implement



A. M. VlK 3,438,669

CLAMP MECHANISM FOR A LIFTING IMPLEMENT A ril 15, 1969 Filed Jan. 16,1967 Sheet F E 5 v INVENTOR' I 44 444 M We BY 2 M April 15, 1969 A. M.VIK 3,438,669 v CLAMP MECHANISM FOR A LIFTING IMPLEMENT Filed Jan. 16,1967 INVENTOR.

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United States Patent 3,438,669 CLAMP MECHANISM FOR A LIFTING IMPLEMENTAlbam M. Vik, New Brighton, Minn., assignor to Inventors EngineeringInc., Fridley, Minn., a corporation of Minnesota Filed Jan. 16, 1967,Ser. No. 609,394 Int. Cl. B66c 1/30; B66f 9/06, 9/18 US. Cl. 29490 9Claims ABSTRACT OF THE DISCLOSURE A mechanical clamp apparatus for alifting implement composed of a framework to which a pair of horizontalparallel arms are pivotally secured at their rearward ends. A jaw ismounted on the forward end of each arm and a link extends toward theside from each arm and is pivotally connected at its free end to theframework to confine the movement of the arms and jaws to an arcuatepath extending centrally then downwardly so that the downward pressureof an object on the jaws causes the jaws to move toward one anotheragainst the object with a pressure greatly exceeding the weight of theobject.

Clamp mechanism for a lifting implement The present invention relates toarticle handling implements and more particularly to a clamp mechanismof the type to be used on an implement having an article supportingmember adapted to raise and lower articles as they are transported fromone location to another. The invention is particularly useful inconnection with fork lift trucks and the like.

In many of the prior clamps of the type used in connection with amaterial handling implement such as a lift truck, the entire forkmechanism on the lift truck must be removed and replaced by the clampmechanism. Making this change, of course, requires a substantial amountof time and effort. It also necessitates the attention of a killedoperator or mechanic for removing the forks and replacing them with theclamp mechanism. A further shortcoming of prior equipment of the typedescribed is the fact that they occupy so much of the area in front ofthe lift truck that they obstruct the operators vision. In order toreliably transport a variety of articles using a clamp of the generaltype described without significant danger that the article beingtransported will inadvertently fall from the clamp mechanism, it isessential to obtain adequate clamping pressure. At the same time, jawsof the clamp must move apart a sufficient distance to easily clear thesides of the load when the jaws are being engaged as Well as when thejaws are being disengaged from the load.

It has been proposed, in the Moss Patent No. 3,180,512, to provide aclamp mechansim for a lift truck composed of members adapted to engagethe forks at their lower ends, a plurality of spaced columns connectedby cross braces and beam members to provide a rigid rectangularframework. A pair of pivots are provided on the forward ends of theframework, an arm member mounted on each pivot and inclined guides areplaced at the rearward end of the framework for receiving the rearwardends of the arms. In operation, downward pressure of the load istransmit-ted to the portion of the arms extending through the guideswhich because of their inclined position force the jaws toward oneanother in direct proportion to the weight of the object being lifted.These prior devices are relatively bulky and employ numerous parts whichhave been eliminated in the invention. Moreover, the clamping pressureis often inade- 3,438,669 Patented Apr. 15, 1969 quate. This deficiencycan be especially troublesome when relatively heavy objects are beingcarried or when the side walls of the object are formed from a rigidmaterial having a particularly smooth surface. It will also be notedthat while increasing the angle of the guides will increase the clampingpressure, the distance the jaws move apart is reduced by a proportionalamount. This is, of course, undesirable particularly where cylindricalor irregularly shaped objects are to be carried. It will also be seenthat ball bearings or other friction-reducing means must be used at therearward end of the arms to prevent excessive friction in the guides.

Another shortcoming of the prior art is the inability of the clampmechanism to easily accommodate objects of different widths or at bestto accommodate objects having certain predetermined sizes as for example22 inches, 24 inches, 26 inches, in short, objects having predeterminedsize differences.

Still a further disadvantage of the prior art is the inability in amechanical type clamp as opposed to a hydraulic or other power actuatedclamp of varying the clamping pressure. Thus, in accordance with theMoss patent the clamping pressure is determined by the angle of theinclination of the guides and the weight of the object being carried.Accordingly, there is no opportunity for varying the clamping pressureto suit the circumstances under which the clamp is being used.

A further problem encountered in some of the prior mechanical typeclamping mechanisms is the difliculty occasionally encountered inengaging the clamp members over the object that is to be carried. Thus,if the full weight of the clamp arms must be overcome to move the clampsto their upward disengaged posit-ion, it often requires considerableefrort and skill on the part of the operator to force the jaws to theupward or disengaged position by engaging them with the object that isto be carried.

A still further shortcoming of some of the prior mechanical clampmechanisms of the type described is the lack of a secure connectionbetween the load-carrying arms and the framework of the clamp. In somecases, the pivotal connection between these members allows the arms tobe shifted a short distance on the longitudinal axis of the clampmechanism.

In view of the deficiencies of the prior art, it is thus one'object ofthe present invention to provide an improved mechanical type clampingmechanism for load lifting and transporting implements which ischaracterized by being rugged in construction, reliable in operation andcapable of being manufactured at a relatively low cost.

Another object is to enable the clamping pressure to be varied inaccordance with the particular operating conditions encountered.

A further object of the invention is the provision of an improvedclamping mechanism of the type described which can be adjusted laterallyfor a continuous infinite number of width settings whereby an object ofany width can be easily accommodated.

A still further object of the present invention is the provision of animproved mechanical clamping mechanism of the type described wherein theclamping pressure can be varied as required.

A further object of the invention is to provide an improved mechanicalclamp of the type described having the capacity to provide a relativelyhigh clamping pressure while at the same time the jaws are free to movea sufficient distance laterally.

These and other more detailed and specific objects of the invention willbe apparent in view of the accompanying specification and drawingswherein:

FIGURE 1 is a plan view of an apparatus embodying the invention.

FIGURE 2 is a side elevational view of the apparatus of FIGURE 1.

FIGURE 3 is a front elevational view of the apparatus.

FIGURE 4 is a partial transverse sectional view taken on line 4-4 ofFIGURE 1.

FIGURE 5 is a transverse sectional view of the apparatus taken on line5--5 of FIGURE 1 on a somewhat enlarged scale with the clamp arms intheir raised position.

FIGURE 6 is a view similar to FIGURE 5 showing the clamp arms in apartially lowered position.

FIGURE 7 is a view similar to FIGURE 6 showing the clamp arms in theirlowered position.

To the accomplishment of the foregoing and related ends, the inventionthen comprises the features hereinafter described in the specificationsetting forth one preferred form of the invention by way of example.

As can be seen in the figures, particularly FIGURES l, 2 and 3, there isprovided a supporting framework indicated generally at 10 composed ofparallel longitudinally extending and horizontally disposed tubularmembers 12 and 14. The member 12 is provided with side, top and bottomwalls to provide a generally rectangular transverse cross section asseen in FIGURE 3. Member 14 is similarly constructed. Each of members 12and 14 has an opening at the rearward end into which a portion of thelift truck (not shown) in this case the forks 16 and 18 are inserted. Itshould be understood that the portions of the forks 16 and 18 shown inthe drawings are the horizontally disposed portions of the fork.Accordingly, the members 12 and 14 engaged upon and conforming to theforks 16 and 18 will also be disposed horizontally. Since the lift truckforks are well known, they will not be described in further detailherein.

During operation when the clamp apparatus of the present invention is tobe used, the forks 16 and 18 are first lifted from about 1-2 inches fromthe ground. Their forward ends are then inserted into the openings atthe rearward ends of the support members 12 and 14. When the forks havebeen fully inserted they are raised the desired distance from the floor.The apparatus is then ready for use.

To the rearward end of the support member 14 is rigidly secured atransversely extending slide member 20 including a horizontally disposedupper section and downward extending side walls. A similar member 22rigidly secured as by welding to the rearward end of the frame member.12 and is telescopically mounted for transverse sliding movement withinthe member 20 as can be best seen in FIGURE 2. To maintain properorientation between parts 20 and 22, a retainer such as a plate 24 iswelded across the bottom of the slide 20. Connected between the members20 and 22 is a turnbuckle 26 composed of the usual center section 28threaded upon bolts 30 and 32 which are affixed to the slide members 22and 20 respectively. The pitch of the threads for each bolt is in theopposite direction as usual so that rotation of the member 28 willeither cause the bolts to move toward one another or to move apart. Asthe bolts are thus moved, the slide members 20 and 22 will moveaccordingly as will the frame members 12 and 14.

Suitably aflixed, as by welding, to the rear of each of the framemembers 12 and 14 and to the front of the slide members 20 and 22 aretwo pairs of laterally aligned bearing blocks 34 and 36 and 38 and 39,the outer ones of which are provided with horizontally disposedtransversely extending slots 40, the long axis of which is orientedlongitudinally of the framework, i.e. parallel to the axis of the forkengaging frame members 12 and 14 (FIGURES 2 and 4-). Within the bearings36 and 38 are provided spherical sockets 4 2. In each socket is mounteda ball 44 with sufficient clearance to enable the ball to move freely.Pivot pins 46 and 48 extend through the left and right pairs of blocksrespectively. To the pin 46 is secured the rearward end of alongiutdinally extending generally horizontally disposed clamp arm 50and to the pin 48 is secured the rearward end of a longitudinallyextending horizontally disposed clamp arm 52. A pair of jaws 55 and 56are secured to the forward ends of the arms in any convenient manner.The lower forward segment of each of the jaws 55 and 56 is cut away at a45 angle as shown at 5 8 and 61 respectively.

To the side of the arms 50 and 52 are rigidly secured laterallyextending longitudinally spaced flanges 54 and 57 respectively. Pins areconnected between these flanges and a pair of links '62 and '66 areconnected for pivotal movement thereon about a longitudinal axis. Thelinks are connected at their outward ends to pins 68 and 70' which arethemselves rigidly aflixed to the frame members 12 and v14 respectivelyby the provision of vertically extending longitudinally spaced pairs offlanges 72 and 74. As can be seen the flanges 72 and 74 are positionedsomewhat rearwardly of the flanges 54 and5'7. The pins and links may bethought of as a means for connecting each arm at a point bet-ween itsrearward end and the jaw for upward and outward swinging movement abouta radius having its center spaced laterally of the arm when the arm isin its lowered position.

Secured rigidly on the free ends of the members 12 and 14 beneath eachof the arms 50 and 52 are support plates designated and 82 in FIGURES 5,6 and 7. The plates 80 and 82 have an appropriate thickness to hold thearms such that the links 62 and 66 are inclined upwardly proceedingtoward the center of the apparatus at a slight angle designated 0 inFIGURE 7. 6 can be any small angle. In practice, an angle of about 5 hasbeen found satisfactory. The links are prevented from falling below ahorizontal position in order to prevent the load from achieving an overcenter position which, if allowed to occur, would make the loaddifiicult to release.

As seen in FIGURES 1, 2, 5 and 6, a resilient means such as identicalsprings 84 and 86 are positioned between the arms and the fork engagingmembers for biasing the arms upwardly. Springs 84 and 86 do not,however, have sufiicient force to elevate the arms but merely exert aforce sufiicient to counterbalance a portion of the weight of the armsand jaws. Thus, the arms will normally rest on the plates 80 and 82.When, however, an object is to be loaded, I have found that bycounterbalancing a portion of the load as described, the arms can bemuch more easily shifted from the lowered to raised positions whenengaged in the sides of the object being loaded. This advantage provedhighly beneficial in allowing loads to be easily and quickly grasped bythe clamp.

The operation of the apparatus Will now be described. As a first step,the forks 16 and 18 are inserted as described at the beginning of theapplication. The turnbuckle 28 is turned so that the jaws 55 and 56 arespaced apart the proper distance to accommodate the object that is to behandled. The lift truck is then driven forwardly until the cut edges ofthe jaws contact the sides of the object that is to be loaded. When thiscontact has been made, the forks 16 and 18 are lowered slightly so thatthe jaws 55 and 56 will be elevated relative to the frame members 12 and14 as the arms 50 and 52 pivot about the pins 46 and 48 until theposition of FIGURE 5 is achieved. In this position it will be seen thatthe jaws are spaced relatively far apart. This is because the arms andjaws travel in a horizontal direction during the last portion of the areabout the pins 68 and 70.

As can be best seen in FIGURE 6 in which arcs of equal size aredescribed about pivot 68 as a center, the vertical projection of theuppermost are a on a horizontal line a defines a horizontal distance oftravel a. However, as the arm moves downwardly through an arc b equal insize to are a, the vertical projection d on horizontal line d will besubstantially smaller than the projection a. Similarly, the projection cof the are c is very much smaller than the projection b. It can thus beseen that in the last portion of their upward movement the arms aredirected laterally. On the other hand, by virtue of the alignment of thelinks 62 and 66 between the jaws and the pivots 68 and 70, the clampingforce on the object suspended between the jaws is many times thedownward force exerted by the object itself on the jaws. Accordingly,very high clamping forces can be achieved. It should be noted that theball and socket joints 42 and 44 universally connect the arms to theframework while at the same time the outward ends of the pins 46 and 48extending through the slots prevent rotation of the arms about their ownaxes.

For proper operation, the arms should be in contact with the plates 80and 82 when a load is placed on the jaws. However, if they are almost incontact with the plates but spaced slightly from them, performance willalmost always be satisfactory. 0n the other hand, if the arms aresubstantially off the plates, say one inch above them, it may bepossible for the load to shift. The preferred practice is therefore tokeep the arms in contact or almost in contact with the plates 80 and 82.This is done with the turnbuckle 26.

Frequently, the clamping pressure must be either increased or decreasedto suit the circumstances encountered. To make this adjustment, e.g. toincrease the clamp ing pressure, the turnbuckle member 28 is turnedappropriately to draw the members 12 and 14 toward one another. Whenthis is done, the load being carried will be partially supported by theplates 80 and 82 and partially by the links 62 and 66.

When the entire weight of the load is just supported by the links,clamping pressure will be maximized. Care should be taken not to elevatethe arms substantially above the plates 80 and 82 for the reasons givenabove. If the clamping pressure is to be decreased, the turnbuckle 28 isturned in the appropriate direction to force the members 12 and 14apart, but the jaws should not be separated sufliciently so that theload is released altogether. When this adjustment is made, the load willbe shifted to plates 80 and 82. Accordingly, the clamping pressureexerted upon the object by the jaws will be decreased.

It is apparent that many modifications and variations of this inventionas hereinbefore set forth may be made without departing from the spiritand scope thereof. The specific embodiments described are given by wayof example only.

I claim:

1. A clamp mechanism for lifting implement comprising in combination asupporting framework, horizontally disposed and forwardly extending armsconnected to the framework by means of a universal joint at theirrearward ends so that the forward ends are free to move betweenreleasing positions spaced relatively far apart and engaged positionsspaced relatively close together, jaws on the forward ends of the armsfor engaging a load and link means connecting the forward ends of thearms and the framework for upward and outward swinging movement of thearms and jaws relative to the framework about two radii having centersspaced laterally of each arm when the arm is in its lowered engagedposition whereby the downward force of the load on the jaws will forcethe jaws toward one another as the arms swing through an area defining aportion of the surface of a cone thereby clamping the load in itsengaged position between the aws.

2. The apparatus of claim 1 wherein said radii are defined by linksconnected to each arm at one end and to the said framework at the otherend at a point located be tween the rearward of the arms and the jaws.

3. The apparatus according to claim 1 wherein the rearward ends of thearms are pivotally and universally connected to the supporting frameworkand a means is provided for preventing rotation of the arms on their ownaxes.

4. The apparatus according to claim 3 wherein a ball and socket joint isconnected between the rearward end of each arm of the supportingframework, a bearing means is supported upon a framework laterally ofeach arm, each such bearing means having a horizontally disposedlongitudinally extending slot therein and means secured to the rearwardend of each arm extends through one such slot to thereby preventrotation of each arm on its own axes.

5. The apparatus according to claim 3 wherein a pair of laterally spacedaligned bearing blocks is provided on the framework at the rearward endof each arm, a pin is secured to the rearward end of each arm and eachsuch pin extends through one pair of said bearings, one bearing of eachpair including a ball and socket joint having said pin extendingtherethrough and the other bearing of each pair includes a horizontallydisposed elongated slot, the opposite end of the pin from the ball andsocket joint being positioned in said slot and the axis of each slotbeing oriented along the longitudinal axis of the clamp whereby the armsare universally mounted at their rearward ends and prevented fromrotating on their own axis by the engagement of the pin in the slot.

6. The apparatus according to claim 1 wherein said supporting frameworkis composed of two portions adapted to slide toward and away from oneanother on a lateral axis, one said arm being mounted on each portionand a means is provided for moving the two portions of the frametogether or apart on said axis and for locking the two frame portions inselected positions on said axis whereby the spacing between the jaws intheir clamped position can be varied as required.

7. The apparatus according to claim 6 wherein the means for changing theposition of the frame portions comprises an adjustable retainer meansfor securing the portion of the framework in a continuous infinitenumber of positions whereby the jaws can be moved to a continuousinfinite number of width settings and the pressure exerted by the jawsupon the object being carried can be adjusted as required.

8. The apparatus according to claim 1 wherein a resilient means isoperatively connected between the framework and the arms for biasing thearms toward an upward position with sufficient force to partiallycounterbalance the weight of the arms and jaws.

9. The apparatus according to claim 1 wherein a pair of flanges aresecured at the outside edge of each of the arms, pins are securedbetween the flanges, links extend from the pins laterally, the free endsof the links are connected between a pair of flanges rigidly secured tothe supporting framework and the pairs of flanges secured to thesupporting framework are positioned slightly rearwardly of thoseconnected to the arms whereby the arms will be free to swing upwardlyand outwardly with no tendency for the links to bind on the pivots.

References Cited UNITED STATES PATENTS 1,807,360 5/1931 Wehr 214-65O2,497,778 2/1950 Cado 74469 2,842,275 7/1958 Kughler 214-653 3,172,6933/1965 Hansen 294 3,194,345 7/1965 Kozak 18751 3,263,516 8/1966 Chisholm74469 3,319,815 5/1967 Uik 214-620 FOREIGN PATENTS 671,3 32 4/ 1952Great Britain.

EVON C. BLUNK, Primary Examiner.

H. C. HORNSBY, Assistant Examiner.

US. Cl. X.R. 214620, 653

